The invention relates to a saw chain for chain saws, and to a particular tie link for such a chain.
An optimally designed saw chain is one that has good wear characteristics, minimal kick-back, and good cutting action. The chain according to the present invention is constructed with these optimal results in mind.
The chain according to the invention presents a general facial area as the chain is traversing the nose of a guide bar (where kick-back can occur) that is substantially as wide as the chain itself, minimizing the possibility that the cutter will become buried in the wood being cut. This wide facial area is provided by constructing a specially configured tie link (i.e. a guard link) that is disposed on the opposite side of the chain from a following cutter link. All other components of the chain may be conventional components, resulting in ease of manufacturing procedures. The guard link does not significantly interfere with the cutting action of the cutter link, and is positioned with respect to the cutter link so that there is good chip clearance and so that any tendency of the chain to "skate", when brought into contact with a smooth cutting surface, is minimized.
A tie link (i.e. guard link) according to the present invention comprises a non-cutting link having a base portion including front and rear rivet receiving openings, and a top portion extending above the base portion. The top portion terminates in a nose portion which is rearward of the entire rear rivet receiving opening (and preferably rearward of the entire base portion of the link), and the center of gravity of the link is located closer to the rear rivet receiving opening than the front rivet receiving opening. The nose has a width substantially greater (e.g. twice as great) as the width of the base portion of the guard link, so as to present a large facial area as the chain of which the link is a part traverses the nose of a guide bar.
A saw chain according to the present invention comprises a series of center drive links, and pairs of side links all pivotally joined to the center links to form an articulated chain.
A first pair of side links comprises a non-cutting tie link to one side of the chain, and a cutter link on the opposite side of the chain from the non-cutting tie link. The cutter link has a base portion including front and rear rivet receiving openings, and a top portion above the base portion and including an upstanding depth gauge at the front of the link, and a cutter tooth rearward of the depth gauge.
The chain further comprises a second pair of side links immediately preceding each cutter link, and comprising a non-cutting tie link on the same side of the chain as the following cutter link, and a non-cutting guard link on the opposite side of the chain from the following cutter link, the guard link being as previously described. The nose portion of the guard link terminates adjacent the depth gauge of the following cutter link, and preferably has a width substantially equal to the width of the guard link base portion plus the width of a center link. When the chain is straight the nose portion of the guard link preferably has a height less than the maximum height of the depth gauge, but the nose of the guard link is constructed so that as the chain goes around the nose of a guide bar (where kick-back can occur) the nose of the guard link is even with, or slightly higher than, the depth gauge. The distance that the nose extends rearwardly of the rear rivet-receiving opening, or base portion, of the guard link, and its position vis-a-vis the following cutter link depth gauge, is dependent upon the particular size (e.g. pitch) of the chain, the configuration of the cutter, particular cutting conditions, and the like. For instance the nose portion of the guard link can be configured so that one can, or cannot, see light between it and the depth gauge of the following cutter link when the chain is straight and viewed from the side, or when the chain is traversing the nose of a guide bar and viewed from the side.
The guard link according to the present invention preferably is constructed from a blank (cut to a predetermined configuration) which is passed through a progressive die system so that the top portion of the link is gradually bent over. That is, the guard link according to the present invention is preferably formed in a manner similar to the manner in which the cutter teeth of cutter links are conventionally formed, except, of course, that there will be no sharpening of any surfaces thereof, and the maximum width of the nose of the link preferably is only about two-thirds the width of the chain.
It is the primary object of the present invention to provide a saw chain, and particular non-cutting tie link therefor, which can minimize kick-back without adversely affecting cutting capabilities of the chain. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.